As a rotating electrical machine, for example, an AC synchronous generator supplies a field coil of a rotor of the generator with a DC current from an outside source to generate a rotating field by rotating the rotor, so that an AC voltage is induced across an armature coil fixed on an outer peripheral side of the rotor. For a current collector portion in the related art serving as an electrical connection portion between the field coil and the outside source, there is a configuration shown, for example, in FIG. 6 and FIG. 7.
FIG. 6 is a partial cross section showing only an upper half of a rotor on a current collector side from a shaft center. Also, FIG. 7 is an enlarged cross section of a portion encircled by an alternate long and short dash line of FIG. 6.
As is shown in FIG. 6, a rotor 31 has a center hole 32a at a center of a rotation shaft 32 and axial leads 33 are disposed in the center hole 32a. The axial leads 33 extend from a main terminal bolt 34 to a pair of radial leads (collector terminal bolts) 35 and are connected to one ends of the respective bolts.
The other end of the main terminal bolt 34 is connected to main field terminal windings 37 held by a press ring 36. The other ends of the radial leads 35 are connected to a pair of slip rings 38a and 38b attached to the rotation shaft 32.
A DC current is supplied to the slip rings 38a and 38b from carbon brushes (not shown) and the current is passed toward the main field terminal windings 37 by way of the radial leads 35, the axial leads 33, and the main terminal bolt 34.
A detail of a radial lead portion will be described with reference to FIG. 7. The radial lead 35 has male screws formed at an upper end side and a lower end side and a smooth intermediate portion. The intermediate portion is surrounded by an insulating sleeve. The lower end side is threaded into a female screw of the axial lead 33 and fixed therein. The upper end side is connected to a connection lead line 41 of the slip ring by a copper nut 39 and an inner copper nut 40. A gasket 43 sandwiched between a seal washer 44 and a gasket bushing 45 is inserted into a radial lead hole 42 provided to the rotation shaft 32. At a position in the vicinity of an outer periphery of the rotation shaft 32, a fastening bolt 46 is fastened to a female screw portion formed in the radial lead hole 42 to compress the gasket 43, so that airtightness is maintained. An interior of a generator is filled with a cooling refrigerant, for example, a hydrogen gas. The hydrogen gas also flows into the center hole 32a of the rotation shaft 32 and fills a clearance between the center hole 32a and the axial lead 33. Hence, the gasket 43 plays a role as a seal that prevents the hydrogen gas from leaking to the outside (see, for example, Patent Document 1).